TC 11S(FREDDY): powerful and compact CAT 4 US approaching the Mascarenes//Invest 99W//Invest 91P//Invest 92S// 1715utc update

JTWC IS ISSUING 12HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 11S(FREDDY).

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: OVER THE PAST 12 HOURS, TROPICAL CYCLONE (TC) 11S HAS CONSOLIDATED WITH A MORE SYMMETRIC STRUCTURE AND WARMER EYE. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SYMMETRIC CORE SURROUNDING A 20NM DIAMETER ROUND EYE WITH A 17.3C EYE TEMPERATURE. ALTHOUGH THE SYSTEM MAY APPEAR ANNULAR AT TIMES, IT IS CLEARLY NOT ANNULAR; CLOUD TOP TEMPERATURES ARE NOT UNIFORM AND A 171248Z SSMIS 91GHZ MICROWAVE IMAGE SHOWS CONVECTIVE BANDING OVER THE WESTERN SEMICIRCLE. ANIMATED WATER VAPOR IMAGERY CONTINUES TO INDICATE RADIAL OUTFLOW AND ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE WITH LOW VERTICAL WIND SHEAR AND WARM (28C) SST VALUES. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON RECENT EWS-G1 SATELLITE IMAGERY AND THE SSMIS 91GHZ IMAGE. THE INITIAL INTENSITY OF 120 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE SUBJECTIVE DVORAK ESTIMATES RANGING FROM 115 TO 127 KNOTS AS WELL AS ADT AND AIDT ESTIMATES OF 122 AND 124 KNOTS. RECENT DMN AND OPEN-AIIR ESTIMATES ALSO SUPPORT THIS ASSESSMENT AND RANGE FROM 115 TO 120 KNOTS.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 11S WILL CONTINUE TO TRACK WESTWARD THROUGH TAU 48 ALONG THE NORTHERN PERIPHERY OF THE STR. AFTER TAU 48, THE SYSTEM WILL TURN WEST-SOUTHWESTWARD AS THE STR REORIENTS TO THE SOUTHEAST WITH THE APPROACH OF A MAJOR SHORTWAVE TROUGH. THIS TROUGH IS EXPECTED TO FILL AND PROPAGATE QUICKLY EASTWARD, WHICH WILL ALLOW TC 11S TO RETURN TO A MORE WESTWARD TRACK NEAR TAU 120. DESPITE DRY AIR ENTRAINING AROUND THE PERIPHERY OF THE SYSTEM AND POSSIBLE UPWELLING COOL WATER, TC 11S REMAINS RESILIENT AND CONTINUES TO TRACK STEADILY WESTWARD AT 14 KNOTS. TC 11S IS EXPECTED TO WEAKEN SLIGHTLY BY TAU 24 BUT IS EXPECTED TO REINTENSIFY SLIGHTLY TO 120 KNOTS BY TAU 48. AFTER TAU 72, STEADY WEAKENING IS ANTICIPATED AS THE SYSTEM APPROACHES MADAGASCAR NEAR TAU 96 THEN RAPID WEAKENING AS THE SYSTEM TRACKS OVER MADAGASCAR.

MODEL DISCUSSION: WITH THE EXCEPTION OF AFUM, WHICH RECURVES THE SYSTEM SOUTHWESTWARD OVER SOUTHERN MADAGASCAR, NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT WITH A 60NM TO 115NM SPREAD IN SOLUTIONS FROM TAU 72 TO TAU 120. THE BULK OF THE EPS AND GEFS SOLUTIONS INDICATE A HIGH PROBABILITY OF LANDFALL OCCURRING OVER CENTRAL MADAGASCAR HOWEVER THERE IS A LARGER SPREAD OF SOLUTIONS THAT EXTEND OVER SOUTHERN MADAGASCAR. THE 170000Z COAMPS-TC ENSEMBLE INDICATES A 60 TO 70 PERCENT PROBABILITY OF MODERATE INTENSIFICATION OCCURRING FROM TAU 24 TO TAU 72 AS THE SYSTEM PASSES NORTH OF PORT MATHURIN AND MAURITIUS.

THE AREA OF CONVECTION (INVEST 99W) PREVIOUSLY LOCATED NEAR 5.7N 135.3E IS NOW LOCATED NEAR 7.7N 131.8E, APPROXIMATELY 163 NM WEST OF PALAU. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A BROAD, DISORGANIZED LOW-LEVEL CIRCULATION WITH DEEP CONVECTION OFFSET IN THE WESTERN SEMICIRCLE. INVEST 99W IS CURRENTLY POSITIONED ALONG THE SOUTHEASTERN EDGE OF AN EXTENSIVE NORTHEAST SURGE FLOW (25-30 KNOTS). ENVIRONMENTAL ANALYSIS INDICATES UNFAVORABLE CONDITIONS WITH HIGH (25- 40KT) EASTERLY VWS AND BROAD DIFLUENCE ALOFT. SST REMAINS CONDUCIVE AT A WARM 28-29C. GLOBAL MODELS ARE IN GENERAL AGREEMENT THAT 99W WILL HAVE LITTLE DEVELOPMENT AS IT TRACKS WEST-NORTHWESTWARD OVER THE NEXT 48 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 10 TO 15 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1005 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS LOW.

GLOBAL MODELS ARE IN GENERAL AGREEMENT THAT 99W WILL HAVE LITTLE DEVELOPMENT AS IT TRACKS WEST-NORTHWESTWARD OVER THE NEXT 48 HOURS.